In coke ovens it is known to provide a battery of horizontal coke-oven chambers each of which can have a height considerably greater than the width and which can be provided at opposite ends with doors or closures which are sealed in the respective doorways by a variety of means. Reference may be had to The Making, Shaping and Treating of Steel, pages 119ff, U.S. Steel Co., Pittsburgh, Pa., 1971.
The doorways of such horizontal coking chambers have closures at opposite ends which can comprise doors which sealingly engage and latch against the continuous door jambs extending around and framing such openings. The doors, moreover, are provided with door plugs which project into the furnace chambers.
Between the door, door plug and door frame, a gas collecting space or passage is formed whereby gases remaining from the coking process and sealed from the atmosphere may be withdrawn.
Fine coal may be coked in horizontal-chamber coking ovens by indirect heating, thereby generating significant quantities of gas. This gas seeks to escape into the atmosphere through the closures or doors at the ends of the chamber, especially immediately following the filling thereof with coking coal substantially to the height of the closures.
There have been numerous proposals seeking to seal the doors so tightly that a minimum of the generally toxic or noxious gases can escape. It should also be noted that such gases are easily combustible and result in problems within the coke oven on this ground as well.
The sealing means generally provide metal-to-metal contact between the closure or door and the door frame.
While such metal-to-metal seals have the advantage of heat resistance, they are not always satisfactory for coke oven purposes since it is not always possible to bring about the requisite good surface-to-surface contact between the sealing members.
Any failure of the seal can result in gases escaping into the atmosphere. Environmental protection requirements mandate that such escape be excluded or minimized and considerable effort has been invested in designing metal-to-metal seals for this purpose. Reference may be had in particular, to U.S. Pat. No. 1,065,370, to German patent document DE-as No. 1,017,590 and to German patent document DE-p No. 24,593.10 aD.
In all of these closure systems, however, the escape of gas from the coking chamber into the atmosphere cannot be completely foreclosed and, in addition, considerable expense and labor must be expended on cleaning the sealing surfaces because tar and graphite condensates tend to accumulate thereon.
While manual cleaning has been practiced for a long while, in recent years efforts have been made to substitute mechanical cleaning. Mechanical cleaning, however, has been found to be less than fully effective in removing accumulations of contaminants from corner regions of the door frame and the door.
One of the problems which arises is due to the fact that conventional metal-to-metal seals require a condensate film for most effective formation of a hermetic barrier. This condensate film tends to form as a result of the pressure fluctuations in the coking oven which can cause a pressure drop such that a precipitation of condensate occurs in the sealing regions. During this pressure drop the sealing members cooled spontaneously, rapidly and to a lower temperature than other parts of the oven, thereby resulting in preferential formation of the condensate film.
After the closure member, i.e. the coke oven door, is set into the door opening and after filling of the chamber with the coking coal, condensate precipitates upon the sealing surfaces until these regions are again brought to a high temperature by the coking process.
It has been found to be a drawback of such systems that the formation of the condensate cannot be controlled. In the region of the bottom of the door, for example, and immediately thereabove, the amount of condensate which forms is excessive, i.e. far more than is necessary to form the sealing film.
On the other hand, in upper regions of the door, the condensate formation may be insufficient to form the requisite film.
At the regions to which there is excess uniform condensate formation, the sealing of the chamber may be more difficult and contamination can occur to a significantly greater degree requiring excessive cleaning.